U.S. Pat. No. 4,296,164, issued to Bemis and McCartan on Oct. 20, 1981 discloses a method of making glass wool blowing insulation including slitting and crosscutting a glass wool blanket. The product didn't perform as well as desired.
U.S. Pat. No. 4,184,643, issued to McCort on Jan. 22, 1980 discloses a method of making glass wool blowing insulation including cutting a glass wool blanket with hollow rotary cutting grids, the cut product passing through the cutting grids into the central portions of the hollow rotary cutters.